Answer: D) It creates a formal and sincere tone.
Step-by-step explanation: The tone of a text or sentence is the author's or speaker's attitude towards the audience, the subject or even the characters of the text. There are many different kinds of tones, like: positive, negative, objective, sad, angry, etc. In the given excerpt from "Nixon Resigns" by Carroll Kilpatrick we can see that the use of language (words like: error, deeply regret, course of events, etc) creates a formal and sincere tone.